1. Field of the Invention
This invention relates to a wind driven sailing system for a boat. More particularly, it relates to a sailing system which powers a boat in the manner of a conventional sail and which also serves as an energy generating source for an auxiliary manner of propelling the boat.
2. Description of the Prior Art
Through evolution sailboats today typically are constructed with an upright elongate mast fixed to the deck or other portion of the boat hull. A forestay typically interconnects the top of the mast or masthead to the bow of the boat and a backstay extends from the masthead to the stern of the boat to thereby brace the mast in the fore and aft directions. Shrouds interconnect the masthead with the hull on each side of the boat to brace the mast in the transverse directions. The mast serves to support a triangularly shaped main sail, with the forward edge of the main sail mounted along the height of the mast to lie closely adjacent the rear or trailing side of the mast. A generally horizontally disposed, rearwardly extending boom is pivotally mounted on a lower portion of the mast to swing about the mast. The boom is adapted to be connected to the main sail along the bottom edge thereof and serves to vary the angle of the sail relative to the hull of the boat as the boom is selectively pivoted about the mast.
The main sail, for instance when the boat is on a reaching course, reacts with the wind to propel the boat through the water. To achieve maximum cruising speed, the sail is pivoted about the length of the main sail in response to the course of the boat and the direction of the wind. If the boat is on a reaching course heading diagonally into the wind, for instance on a port reach, the trailing edge of the sail is permitted to extend rearwardly from the mast towards the starboard side of the boat to thereby produce an airfoil shape. The sail divides the wind moving past it into twin currents of air which move at unequal velocities due to the sail's air foil shape. Because the air traveling along the leeward side of the sail has a further distance to travel then the air moving along the windward side of the sail, the air at the leeward side of the sail must move faster in order to reach the sail's trailing edge at the same time as the wind traveling along the windward side of the sail. It is a well-known law of physics that as a fluid accelerates it exerts less pressure on the surfaces which it flows past. Thus, the air pressure on the leeward side of the sail is relatively less than the pressure on the windward side of the sail, thereby producing a continuum of individual force components acting towards the leeward of the sail in a direction normal to the surface of the sail. The totality of all of the individual forces acting on the sail produces a lateral or heating force component acting laterally of the boat tending to push the boat sideways and a thrust force component acting along the length of the boat tending to push the boat forwardly and thus permitting the boat to travel diagonally into the wind. Thus, by steering a zig-zagged pattern, it is possible for a sailboat to actually reach an upwind destination.
When sailing laterally of the direction of the wind, with the wind blowing from the port side over the beam, the sail is opened up further than when sailing into the wind so that the trailing edge of the sail actually extends laterally sideways beyond the starboard side of the boat. The reaction between the wind and the sail is essentially the same as that described above when steering a course diagonally into the wind; however, when sailing laterally of the wind a larger forward propelling, thrust force is produced while a smaller transverse or heeling force is produced.
When running, or sailing in the direction of the wind, the sail is permitted to extend essentially perpendicularly to the length of the boat so that the boat's forward movement comes simply from the wind pushing against the sail.
However, no matter what course one desres to sail relative to the wind, movement of the boat is always dependent on the existence of a wind. Without any wind a sail simply cannot provide any propulsion force. Furthermore, a sailboat that is powered only by sails is difficult to maneuver in close quarters. Thus, when entering and leaving crowded areas, such as a marina, an auxiliary power source, such as an outboard motor, is commonly employed. Moreover, even if the sails of a boat are rigged for foul weather, the boat propelled only by sails is difficult to handle during a storm when the seas are rough and the wind is blowing at a high speed.
Thus, most boats cannot rely solely on sails as their only source of propulsion. Rather, an auxiliary power source, such as an inboard or outboard motor powered by gasoline, diesel or an electric battery, is usually required to augment the sail. But with the escalating price of petroleum fuels, the expense of operating even an auxiliary gasoline or diesel engine for a sailboat, has been increasing dramatically. Furthermore, because of the inherent inflammability of petroleum fuels, boating regulations only permit a limited quantity of fuel to be carried on a boat unless adequate structure and ventilation regulations are met. It is usually economically impractical to build many smaller size sailboats in such a manner to meet these regulations; thus, the limited amount of fuel which these boats are allowed to carry seriously hampers their maximum cruising range.
Rather than utilizing a conventional sail, in another type of wind powered boat, a windmill is used to propel the boat. In one such type of boat the rotating propeller of the windmill is mechanically coupled to drive a conventional ship's screw. Examples of this type of boat are disclosed by Dobbins U.S. Pat. No. 2,408,412; and by Lindsey U.S. Pat. No. 3,964,426.
Another type of windmill boat is disclosed by Dore U.S. Pat. No. 2,261,434 wherein a windmill has been utilized to essentially replace the gasoline engine of an outboard motor. As with the two previously discussed patents, the windmill is mechanically coupled to the well-known propeller of the outboard motor.
Another example of a windmill type of boat is disclosed by Maki et al. U.S. Pat. No. 1,506,847, wherein the propeller of a windmill is mechanically coupled to a pair of paddles which extend downwardly into the water at the rear of the boat. The paddles pivot back and forth about their upper ends, which upper ends are pivotally connected to the boat to thereby push the boat through the water. The paddles are designed to also alternatively open and close so that when the paddle is pivoting rearwardly, the plane of the paddle extends transversely of the length of the boat to create a forward propulsion force. However, when the paddle is pivoting forwardly toward the boat, the paddle lies in a plane longitudinally of the boat thereby causing very little drag in the water.
As discussed above with respect to boats powered by a conventional sail, windmill powered boats also require the existence of a wind for propulsion. Thus, when no wind is blowing, boats utilizing windmills have no source of propulsion.